AA 2460 23.5 gr.64 gr.PP was 3.5
inch group at 100 yds. Well back to the bench .
Try a loading a dummy round without a crimp. Put it under your load and see if your C.O.A.L. changes. If not try not using a crimp.DPMS Orical 16 inch barrel 1:9 ROT with trigger job, Wolf brass 64 gr PP today, I tryed CCI 400 primers ,IMR 4198 results not good . Benchmark results not good , win 748 results decent , IMR 4064 seem to be the best. Win 748 2 inch at 100 yds. IMR 4064 I got 1 inch group at 100 yds. Had 1 slam fire.
This combination of IMR 4064 Win.64 gr PP I what use on hogs with bolt action, It done well in my AR , the old powders can still shine.Try a loading a dummy round without a crimp. Put it under your load and see if your C.O.A.L. changes. If not try not using a crimp.
Not crimping dropped about a 1/4" off my group.
You could always try IMR3031.
My AR likes 4064 also. I feel for you. It sucked trying to get it in the case.I have AA 2460, Benchmark,Win 748 I've ben
working loads up with theses 3 powders I've got 2 to 2.5 in. groups at 100 yd. The imr 4064 was able to get 1 1/8 in.at 100 yd.